Stamp Duty Land Tax on residential property

SDLT runs three regimes side by side, and each has its own shape — most wrong answers apply one regime's shape to another's numbers. The STANDARD bands are progressive, like income tax: each band's rate touches only the slice of price inside it, and applying the top rate reached to the whole price is the pre-2014 'slab' error, kept alive in distractors precisely because the old system worked that way. The SURCHARGE for buying a residential property while already owning another is the opposite shape: 5% charged FLAT on every pound of the price, nil band included, stacked on top of the progressive calculation — a progressive system with a flat rider bolted on. FIRST-TIME BUYER relief is a third shape again: its own band structure (nothing up to £300,000, 5% on the excess), not a discount on the standard bands — and it ends at a CLIFF: one pound of price above £500,000 and the relief is lost on the entire purchase, not just the excess. Pre-empt the natural blends before the exam serves them: the surcharge is never 'only on the top band'; the relief never survives above its maximum price; and the two can't meet — someone buying an ADDITIONAL property is by definition not a first-time buyer, so relief never cancels a surcharge. Rounding, if asked: SDLT rounds down to the whole pound.